Functional group chemistry at the zirconocene backbone:: Addition reactions to pendant alkynyl substituents

The nickel-catalyzed cross-coupling of 2-bromoindene with propynyl- or (phenylethynyl)magnesium bromide gives the corresponding 2-alkynyl-substituted indenyl ligands. Subsequent deprotonation and transmetallation with the bis(tetrahydrofuran) zirconium tetrachloride adduct yields the corresponding bis(2-alkynylindenyl)dichloridozirconium complexes 4a and 4b, which cleanly add a Co-2(CO)(6) unit to their pairs of alkynyl substituents to give the dimetallic complexes 5a and 5b. Complex 5b was characterized by an X-ray crystal structure analysis. Complex 4a adds HB(C6F5)(2) to the alkynyl substituents to yield a mixture of alpha- and beta-(borylalkenyl)metallocenes. Activation of these complexes with MAO gives active ethene polymerization catalysts, and the 4a,4b,6a/MAO systems are also active in propene polymerization. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).